Abstract
Although the metaphosphate glasses R( containing high concentrations of rare-earth ions have potentially important applications in optical communications and laser technologies, there is little previous information about their structures. To establish the essential features of the structure of such a glass, the complementary techniques of x-ray diffraction and extended x-ray-absorption fine structure (EXAFS) have been used upon the terbium metaphosphate glass, having a composition found by electron probe microanalysis to be ((. The combination of the two techniques allows for a more comprehensive interpretation of the structural data, since each method suffers from differing analytical problems, notably the composite radial distribution function obtained from diffraction, and the present lack of a good calibrant for the EXAFS experiment. The diffraction results prove to be consistent with a network model dominated by a phosphate glass skeleton constructed from tetrahedra bonded to adjacent tetrahedra via bridging oxygen atoms. This previously unestablished structural model has been used formerly to interpret a wide range of thermal, ultrasonic, and optical properties. The EXAFS, being an atom-type specific probe, have provided the more direct information on the local structure at the rare-earth ion site in vitreous ((: notably a strong correlation in 2.25 Å, associated with an average coordination number of 7±1 for oxygen atoms surrounding a ion.
- Received 1 September 1994
DOI:https://doi.org/10.1103/PhysRevB.51.5739
©1995 American Physical Society